This invention pertains to a welding fixture for supporting elongated structures such as tubes during welding of the structures. It pertains particularly to such a welding fixture for supporting elongated tubes while depositing weld metal over the whole exposed face surface of the tubes, and to a method of producing undistorted metal clad tubular panels.
In municipal solid waste (garbage burning) boilers, the combination of high temperatures above 1000 degrees F, high gas velocity and an extremely erosive and corrosive environment causes boiler tubes to wear very rapidly. Consequently, repairs or replacement of such boiler tubes is the most costly problem facing the municipal solid waste boiler industry today. In addition, the lengthy boiler downtime, lost service and lost revenue caused by such repairs cannot be tolerated. These problems are caused by boiler tube corrosion and erosion produced by burning municipal garbage. The present technical solution to this problem is to completely cover the boiler tubes in the furnace area with an anti-erosive and anti-corrosion metal cladding material such as Inconel 625, which is deposited on the tubes by manual welding in place using the gas metal arc process.
However, a major quality concern for such metal clad welding of boiler tubes is that the heat input is high and it produces severe warpage, inconsistent stresses, and poor welds due to the extremely difficult positions and the inability to maintain a uniform weld deposition thickness on the surface being clad welded. Although the prior art such as U.S. Pat. Nos. 3,596,041 to Frusi et al and 3,895,209 to Moriki et al has disclosed some arrangements for depositing weld metal on rotary machine elements, they do not disclose procedures for preventing distortions in welding elongated relatively thin elements by having the elements rigidly supported by a central rigid rotatable welding fixture. These welding problems are advantageously overcome by this invention, which provides a special welding fixture and a method for accomplishing the needed weld metal cladding of elongated structures such as tubes while being rigidly supported by the welding fixture.